Hi, I’m new to Blender (using version 2.54 and the internal renderer), and I’m trying to use a HDR sky map to obtain a realistic lighting setup.
Unfortunately it seems that the way I configured it, the Sky texture only emits specular light, while ambient lighting is limited to crude constant-color or color-gradient approximations (“Horizon color” and “Ambient color”).
For example, this is with Horizon color and Ambient color set to black, and indirect lighting and AO enabled (additive mode):
Clearly the illumination is uniform white, whereas I would expect more light to come from the top, and I would expect several hard shadows to appear due to the point sources in the skymap.
Setting AO to multiply mode removes the uniform illumination, but then the only ambient light comes from the little amount of light reflected by the monkey head:
So is what I’m looking for impossible? Did I miss a rendering option? Are there other renderers that are capable of doing this? Or would I be forced to try to replicate the sky map by painstakingly placing lamps at the location of all point sources?
There is a bit of graininess involved. In your scene you were trying to use the indirect lighting method, but it seems as if Blender only uses environment lighting in raytrace mode and not in approximate. There is no need, really for the AO since AO will be calculated at a certain distance using the environment lighting option, but I did use it in the render above.
I would have to say that if you want a good quality render with environment lighting, thus global illumination, I would go with Yafaray. There is an exporter available for 2.5, you just have to look for the experimental stuff. I have used it with 2.54 64bit quite often. You just have to install it in the addons area of Blender and they will tell you how on Yafaray.org. Someday Blender Internal may get up to snuff, but it’s not there yet. It works great some times for this type of thing and others, not so much, but for consistency’s sake, try Yafaray for this. Not saying it can’t be done, but my recent experiments have shown that you may wait quite a while.
Trying the scene with Yafaray though seems to be tricky right now since the IBL portion and the texture is giving me fits.
UPDATE: Not getting Yafaray to work with HDR images atm… so…
Good catch, the relevant issue was that I was using Approximate gathering rather than Raytrace, and that’s what made the ambient lighting uniform. However even with Samples set to the max (32x32) the raytraced images are really unusably grainy, and the render is slow.
I think the problem comes from the fact that the spotlights in the HDRI of St Peter’s Basilica are really small, and the Monte-Carlo sampling isn’t smart enough to handle them well. The simplest fix would be something like a Python script that automatically converts a skymap into a set of point sources and area sources that are a good enough approximation for diffuse lighting
